As various digital apparatuses are adapted, the use of a DSP (Digital Signal Processor) increases, which is capable of more efficiently processing a digital signal in real time as compared to a micro-controller provided so as to control a microprocessor or a certain apparatus. The DSP is a kind of a microprocessor which includes a hardware-based multiplier capable of performing calculation at a very high speed in real time in a digital signal process field. Based on their internal structures, the DSP may be classified into a universal type DSP simply formed of a DSP core, and an exclusive type DSP having an input and output (I/O) function and a control program stored in a DSP core, with the input and output function and control program being proper to an audio process, a communication process, an image process, a digital control, and a high speed calculation. Recently, a micro-controller type DSP having a micro-controller DSP has been developed for the use in a certain digital apparatus. The above DSP has improved parallel process, multiple processing functions and communication functions, so that the field of its use is expanded.
The most serious problems lying in the use of digital data by almost apparatuses are a security problem such as data duplication, modulation and hacking. The DSP is well adapted to the process and communication of a digital data but is not capable of directly overcoming the security problems such as digital data duplication, modulation and hacking. Therefore, an additional security module is installed at each digital apparatus which uses the DSP.
However, in the case that data are modulated or hacked in other regions, not in a specific region, the security function does not work, so that the data may be leaked when monitoring an internal data transfer path.